1. Field of the Invention
The present invention relates to a liquid ejection head, a method for preventing accidental non-eject using the ejection head and a manufacturing method of the ejection head, and more particularly, a liquid ejection head for ejecting extremely minute liquid droplets.
2. Description of the Related Art
The ink-jet printing system is known as a system for ejecting liquid such as ink used currently. This ink-jet printing system includes a method using electrothermal converting element (heater) as eject energy generating element for ejecting ink droplet and a method using piezoelectric element, and both methods permit to control the ejection of the ink droplet by means of an electric signal.
For instance, the principle of an ink droplet ejection method using the electrothermal converting element consists in boiling ink instantly in the proximity of the electrothermal converting element by delivering an electric signal to the electrothermal converting element, and rapidly ejecting ink droplets by a sudden bubble growth caused by the phase change of the ink at that time. The principle of the ink droplet ejection method using the piezoelectric element consists in changing the piezoelectric element by delivering an electric signal to the piezoelectric element, and ejecting ink droplets by the pressure caused at the time of this displacement of the piezoelectric element.
A system for ejecting liquid by communicating formed bubbles with the atmosphere is known as a liquid ejection method using the electrothermal converting element. The practical application of this system is disclosed in European Patent Publication No. 0454155. The invention described in such patent publication is made by pursuing the cause of splash caused by bubble explosion or unstable droplet formation and concerns a liquid ejection method comprising the steps of generating a bubble in a liquid passage by a temperature elevation suddenly exceeding the core boiling by delivering thermal energy to the liquid passage and communicating the bubble with the atmosphere near the ejection opening of the liquid passage. In such a liquid ejection method of atmosphere communication from the viewpoint of uniformity during bubble growth and bubble communication with the atmosphere, a so-called side shooter structure liquid ejection head, wherein the ejection opening is disposed in a position opposed to the electrothermal converting element is preferable for stable liquid ejection.
In such an ink-jet printing system, a still higher image quality, a higher resolution and a higher printing speed are required.
However, in the high quality image formation using the side shooter structure liquid ejection head mentioned above, it was found that the communication property between a bubble and the atmosphere begins to affect droplet ejecting direction according to the volume decrease of droplet to be ejected. Particularly, when the ejected liquid volume is reduced to 20xc3x9710xe2x88x9215m3 or less, the trailing (liquid connecting the liquid passage with the main droplet of liquid droplet) and satellite droplet formed by this trailing affect the image quality, and moreover, atomized ink attaches to the surface to be recorded of the printing media and decreases the printing quality, creating a new problem.
The Applicant proposes an excellent ejecting method for resolving the new problem mentioned above using the liquid eject method by the atmosphere communication method. The method is excellent in that it allows one to achieve a high image quality printing with less ejection slippage, by ejecting liquid by communicating a bubble with the atmosphere for the first time in the bubble volume reduction stage, in the so-called side shooter structure liquid ejection head. The inventors have studied to achieve higher resolution and higher quality printing, and found that it is desirable to realize a constantly stable ejection by the ejection method mentioned above, against variable factors such as foaming variation under a high driving frequency, or proprietary variation of nozzles arising in the manufacturing stage. As the result of the empirical analysis of the liquid ejection method mentioned above, the inventors have newly found that in an ejection method wherein liquid is ejected in the defoaming step, it is important to stabilize the liquid movement against variable factors in the whole head arrangement, including not only the ejection opening surface, but also the ejection opening portion forming the ejection opening including the ejection opening surface, and further the eject means and the liquid passage.
The inventors did research on arrangements for suppressing slippage in the droplet ejecting direction, in particular those involving the ejection opening shape, and discovered Japanese Patent Application Laid-open No. 4-39049 (1992). The Patent Publication describes an arrangement wherein the opening section is petal-shaped, in a developer ejection apparatus having a opening section for ejecting developer, a means for ejecting developer from the opening section and a passage where developer flows. However, this Patent Application recognizes as problems that xe2x80x9can extremely unstable behavior occurs during the developer eject due to a distinct boundary between opening sections and non-opening sections of a circular nozzlexe2x80x9d, and that xe2x80x9ca trajectory flexion occurs due to the entrainment by developer attached to the outer periphery of the circular nozzle at the moment when the developer is ejectedxe2x80x9d. In other words, it only intends to make uniform the adhesiveness of the ejection opening surface, and does not satisfy the intent of the present invention mentioned above that consists in considering the cause of ejection slippage, including the ejection means and the liquid passage.
Especially, among liquid ejection heads of the side shooter type, in a composition wherein the liquid passage between the ejection opening and the heat resistance element is surrounded by a wall surface forming the passage sidewall except the direction toward the liquid chamber (refer to FIGS. 69-72), bubbles happen to stagnate for some reason in the corner of a volume surrounded by the wall surface forming the passage sidewall. As the result of absorption of the ejecting power at the moment of foaming by this bubble stagnation, liquid ejection may become unstable, ejection speed lower, ejection flow smaller and ejection direction deviated.
If the opening area of the ejection opening of the liquid ejection head is reduced, for realizing a higher image quality and a higher resolution as mentioned above, ejection may be obstructed by an ink droplet attached to the ejection opening surface for some reason. In particular, in the liquid ejection head using the atmosphere communication system mentioned above, a non-eject (called accidental non-eject hereinafter) occurs when the ejection opening is obstructed by an ink droplet, and a white line may appear during the image formation, because that ejection opening does not engage in the printing.
The Inventors have also examined in detail the phenomena mentioned above, and found that the accidental non-eject is a phenomenon of a single ejection opening, and once a non-eject state occurs, it is hard to recover from it if suction or other recovery means are not used.
Moreover, the inventors have obtained new findings that the whole head arrangement including not only the ejection opening surface, but also the ejection opening portion forming the ejection opening including the ejection opening surface, and further ejecting means and liquid passage is important, to such bubble stagnation or accidental non-eject, too.
The present invention, devised as the result of devoted study by the inventors has a main object to provide a liquid ejection head, allowing one to realize a globally excellent liquid ejection that can meet requirements such as still higher image quality, higher resolution and higher printing speed, by taking into consideration the whole head composition including the i ejection opening portion forming the ejection opening including the ejection opening surface, and further the ejection means and the liquid passage, and a manufacturing method of the head.
To be more specific, the first object of the present invention is to provide an excellent liquid head that can stabilize the liquid ejecting direction against variable factors such as foaming variation under a high driving frequency, or proprietary variations of nozzles arising in the manufacturing stage.
The second object of the present invention is to provide an excellent ejection head that can effectively prevent or control the aforementioned accidental non-eject, and a method of accidental non-eject prevention using the head.
The third object of the present invention is to provide an excellent ejection head that can stabilize the ejecting direction and effectively prevent or control the aforementioned accidental non-eject, while allowing for ejection opening variations arising in the manufacturing stage.
The fourth object of the present invention is to provide a liquid ejection head of complicated but easily formable shape, that can realize a single object, or combined complex objects mentioned above and a manufacturing method of the liquid ejection head.
The fifth object of the present invention is to provide a liquid ejection head that is rapid in meniscus vibration convergence, and excellent in refill performance, of the so-called side shooter type, among heads for ejecting liquid by generating bubbles in liquid droplets.
The sixth object of the present invention is to provide an excellent liquid ejection head that can suppress the ejection of unstable liquid due to bubble embracing, in the so-called side shooter type liquid ejection head, among heads for ejecting liquid by generating bubbles in liquid droplets.
The other objects of the present invention can be understood from the following description, and the present invention can attain any complex object by an arbitrary combination of the individual objects.
Concrete means of achieving various objects mentioned above can be understood from the following description.
A liquid ejection head according to the first aspect of the present invention is characterized in that a liquid ejection head, for causing liquid state change by applying thermal energy to a liquid, to generate bubbles, and for ejecting the liquid by the pressure of the thus generated bubbles, comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to lead liquid to the ejection opening portion; and
a heat resistance element disposed at the liquid passage, for generating thermal energy to be used for ejecting liquid from the ejection opening; wherein
the liquid is ejected in the volume reduction stage after the bubbles have grown to maximum volume; and
a plurality of grooves, which are distributed around the center of the ejection opening and extend in the ejecting direction of the liquid, and are disposed at the ejection opening portion. Thereby, this composition allows one to achieve the first object and meet such requirements as still higher image quality, higher resolution and higher printing speed.
In the liquid ejection head according to the first aspect of the present invention, the liquid may well be ejected by communicating a bubble with the atmosphere for the first time in the bubble volume reduction stage, wherein the gravity center of a polygon defined by connecting center sections of mutually adjacent grooves may correspond approximately to the gravity center of a polygon defined by connecting base sections of the grooves, and six or more grooves may be provided. Top sections and base sections of the groove may constitute respectively a minute curved surface, and the angle defining the groove top section may be within a range from 30 degrees (included) to 90 degrees (included). A liquid chamber to supply the liquid passage with liquid may be disposed, the ejection opening may be disposed at a position opposed to the heat resistance element, and the liquid passage between the ejection opening and the heat resistance element may be surrounded by wall surfaces defining the sidewall of the passage except for the direction toward the liquid chamber. In this case, the top section of at least one of the plurality of groove may be disposed in the direction toward the liquid chamber, or disposed in the direction toward a corner section of a volume surrounded by the wall surfaces composing the passage sidewall. A plurality of grooves may be disposed substantially in line symmetry with respect to a line passing through the ejection opening center, from the liquid chamber to the ejection opening.
A liquid ejection head according to the second aspect of the present invention is characterized in that a liquid ejection head comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to lead liquid to the ejection opening portion; and
an ejection energy generation means disposed at the liquid passage, and used for ejecting liquid from the ejection opening; wherein
grooves extending in the liquid ejecting direction are disposed at the ejection opening portion, for preventing droplets deposited on a face defining the ejection opening from obstructing the ejection opening; and
the ejection opening portion is 7 xcexcm or more in thickness, and the section of the groove at the ejection opening surface is 30 xcexcm2 or less. Thereby, this composition allows one to achieve the second object and meet the requirements such as still higher image quality, higher resolution and higher printing speed.
In the liquid ejection head according to the second aspect of the present invention, tops and bases of the groove may constitute respectively a minute curved surface. The angle defining the groove top may be within a range from 30 degrees (included) to 90 degrees (included). The liquid ejection head may comprise the plurality of grooves distributed in respect to the center of the ejection opening. In this case, the gravity center of a polygon defined by connecting center portions of mutually adjacent grooves may correspond approximately to the gravity center of a polygon defined by connecting bases of the grooves. The ejection energy generating element may be a heat resistance element for generating thermal energy, causing liquid state change by applying thermal energy to the liquid, generating a bubble, and ejecting the liquid by the pressure of the thus generated bubble, and the liquid may be ejected in the volume reduction stage after the bubbles have grown to maximum volume.
A liquid ejection head according to the third aspect of the present invention is characterized in that a liquid ejection head comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to lead liquid to the ejection opening portion; and
an ejection energy generation means disposed at the liquid passage, and used for ejecting liquid from the ejection opening; wherein
grooves extending in the liquid ejecting direction are disposed at the ejection opening portion, the groove being capable of generating a capillary force larger than the adhesive force due to the surface tension of liquid attached to the ejection opening surface. Thereby, this composition allows one to achieve the second object and meet such requirements as still higher image quality, higher resolution and higher printing speed.
In the liquid ejection head according to the third aspect of the present invention, the groove may be provided with a liquid retaining area to retain liquid temporarily. The ejection energy generating element may be a heat resistance element for generating thermal energy, causing liquid state change by applying thermal energy to the liquid, generating a bubble, and ejecting the liquid by the pressure of the thus generated bubble, and the liquid may be ejected in the volume reduction stage after the bubble has grown to its maximum volume. A plurality of the grooves may be distributed around the ejection opening center. In this case, the gravity center of a polygon defined by connecting center portions of mutually adjacent grooves corresponds approximately to the gravity center of a polygon defined by connecting bases of the grooves.
A liquid ejection head according to the fourth aspect of the present invention is characterized in that a liquid ejection head comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to introduce liquid to the ejection opening portion; and
an ejection energy generation means disposed in the C liquid passage, and used for ejecting liquid from the ejection opening; wherein
grooves extending in the liquid ejecting direction are disposed at the ejection opening portion; and
in the ejection opening side end section of the groove, the area near the top of the groove is relatively convex in the liquid ejecting direction, compared to the other areas of the ejection opening surface.
In the liquid ejection head according to the fourth aspect of the present invention, the groove may be provided with a liquid retaining area to retain liquid temporarily. The gravity center of a polygon defined by connecting center portions of mutually adjacent grooves may correspond approximately to the gravity center of a polygon defined by connecting bases of the grooves. The adhesiveness of the ejected liquid to the surface over which the groove of the ejection opening portion extends may be relatively good compared to the adhesiveness of the liquid to the face forming the ejection opening. The ejection opening portion may be 7 xcexcm or more in thickness, and the section of the groove at the ejection opening surface may be 30 xcexcm2 or less. A plurality of the grooves may be distributed in respect of the ejection opening center. In this case, the ejection energy generating element may be a heat resistance element for generating thermal energy, causing liquid state change by applying thermal energy to the liquid, generating a bubble, and ejecting the liquid by the pressure of the thus generated bubble, and the liquid may be ejected in the volume reduction stage after the bubble has grown to its maximum volume.
A method for preventing accidental non-eject due to liquid deposited on the ejection opening of a liquid ejection head according to the fifth aspect of the present invention is characterized by in that it comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to introduce liquid into the ejection opening portion; and
an ejection energy generation means disposed at the liquid passage, and used for ejecting liquid from the ejection opening; wherein
grooves extending in the liquid ejecting direction are disposed at the ejection opening portion; comprising steps of:
sucking liquid in the liquid passage into the groove, after the liquid is ejected from the ejection opening portion by the energy generation means;
taking liquid deposited on the face defining the ejection opening into the groove; and
moving liquid deposited on the face defining the ejection opening to the liquid passage side without obstructing the ejection opening, by the contact, in the groove, of liquid in the liquid passage and liquid deposited on the face defining the ejection opening.
Thereby, this composition allows one to achieve the third object and meet such requirements such as still higher image quality, higher resolution and higher printing speed.
In the method for preventing accidental non-eject due to liquid deposited on the ejection opening of a liquid ejection head according to the fifth aspect of the present invention, the groove may be provided with a liquid retaining area to retain liquid temporarily, and the method may comprise the step of temporarily retaining liquid in the area. A plurality of the grooves may be distributed in respect of the ejection opening center.
A liquid ejection head according to the sixth aspect of the present invention is characterized in that a liquid ejection head comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to introduce liquid to the ejection opening portion; and
an ejection energy generation means disposed at the liquid passage, and used for ejecting liquid from the ejection opening; wherein
the ejection opening portion is formed by etching; and
grooves extending in the liquid ejecting direction are disposed at the ejection opening portion. Thereby, this composition allows one to achieve the fourth object and meet such requirements as still higher image quality, higher resolution and higher printing speed.
In the liquid ejection head according to the sixth aspect of the present invention, the ejection opening portion may be 7 xcexcm or more in thickness, and the section of the groove at the ejection opening surface may be 30 xcexcm2 or less. A minute protrusion section protruding from the groove topside to the base side, may be provided in the liquid passage side of the groove. The groove may be tapered, so that the opening section area of the section along the face having the ejection opening increases from the ejection opening side to the liquid passage side. Tops and bases of the groove may constitute respectively a minute curved surface. The ejection opening side end section of the groove, the area near the top of the groove may be relatively convex to the liquid ejecting direction, compared to the other areas of the ejection opening surface.
A manufacturing method of a liquid ejection head according to the seventh aspect of the present invention is characterized in that it comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to introduce liquid to the ejection opening portion; and
an eject energy generation means disposed at the liquid passage, and used for ejecting liquid from the ejection opening;
wherein the method comprises an etching step for forming the ejection opening portion and grooves extending in the liquid ejecting direction by etching, using an ejection opening forming mask provided with a plurality of convex sections and concave section distributed in respect to the ejection opening center.
In the manufacturing method of a liquid ejection head according to the seventh aspect of the present invention, the manufacturing method of a liquid ejection head may further comprise steps of:
depositing a water-repellent layer on the surface of a member composing the ejection opening portion, before the etching step; and
removing the water-repellent layer with the member composing the ejection opening portion according to the ejection opening configuration in the etching step. The manufacturing method of a liquid ejection head may further comprise a step of:
forming a minute protrusion section protruding from the groove topside to the base side, in the liquid passage side of the groove, in the etching step. The manufacturing method of a liquid ejection head may comprise a step of:
forming a tapered groove, so that the opening section area of the section along the face having the ejection opening increases from the ejection opening side to the liquid passage side, in the etching step. The manufacturing method of a liquid ejection head may comprise a step of:
forming, in the ejection opening side end section of the groove, the area near the top of the groove relatively convex to the liquid ejecting direction, compared to the other areas of the ejection opening surface, in the etching step.
A liquid ejection head according to the eighth aspect of the present invention is characterized in that it comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to introduce liquid to the ejection opening portion;
an ejection energy generation means disposed at the liquid passage, and used for ejecting liquid from the ejection opening; and
a liquid chamber to supply the liquid passage with liquid, wherein state change of the liquid is caused by applying thermal energy to the liquid, a bubble is generated, and the liquid is ejected by the pressure of the thus generated bubble;
the liquid passage between the ejection opening and the heat resistance element is surrounded by wall surfaces defining the sidewall of the passage except for the direction toward the liquid chamber; and
grooves having the top thereof in the direction toward the liquid chamber, and extending to the liquid ejecting direction are provided. Thereby, this composition allows one to achieve the fifth object and meet such requirements as still higher image quality, higher resolution and higher printing speed.
A liquid ejection head according to the ninth embodiment of the present invention is characterized in that a liquid ejection head comprises:
an ejection opening portion provided with an ejection opening to eject liquid;
a liquid passage to communicate with the ejection opening portion and to introduce liquid to the ejection opening portion;
an ejection energy generation means disposed at the liquid passage, and used for ejecting liquid from the ejection opening; and
a liquid chamber to supply the liquid passage with liquid, wherein
state change of the liquid is caused by applying thermal energy to the liquid, a bubble is generated, and the liquid is ejected by the pressure of the thus generated bubble;
the liquid passage between the ejection opening and the heat resistance element is surrounded by wall surfaces defining the sidewall of the passage except for the direction toward the liquid chamber; and
grooves having the top thereof in the direction towards a corner portion of a volume surrounded by wall surfaces defining the sidewall of the passage, are provided. Thereby, this composition allows one to achieve the sixth object and meet such requirements as still higher image quality, higher resolution and higher printing speed.
The present invention can provide a liquid ejection head, allowing one to realize globally excellent liquid ejection that can meet requirements such as still higher image quality, higher resolution and higher printing speed, by taking into consideration the whole head composition including the ejection opening section forming the ejection opening including the ejection opening surface, and further the ejection means and the liquid passage, and a manufacturing method of the head.
To be more specific, the present invention can provide an excellent liquid head that can stabilize the liquid ejecting direction against variable factors such as foaming variation under a high driving frequency, or proprietary variations in respective nozzles arising in the manufacturing stage.
An excellent ejection head, that can effectively prevent or control accidental non-eject, and a method of accidental non-eject prevention using the head can be provided.
An excellent ejection head that can stabilize the ejecting direction and effectively prevent or control the aforementioned accidental non-eject, while allowing for ejection opening variations arising in the manufacturing stage can be provided.
A liquid ejection head of complicated but easily formable shape that can realize either a single object or the combined complex objects mentioned above, and a manufacturing method of the liquid ejection head, can be provided.
A liquid ejection head that is rapid in meniscus vibration convergence, and excellent in refill performance, in the so-called side shooter type liquid ejection head, among heads for ejecting liquid by generating bubbles in liquid droplets can be provided.
An excellent liquid ejection head that can suppress the eject of unstable liquid due to bubble embracing, in the so-called side shooter type liquid ejection head, among heads for ejecting liquid by generating bubble in the liquid droplet can be provided.
In the present invention, the xe2x80x9cejection openingxe2x80x9d means the head surface opening area, and designates, in case of a plate where openings are formed for ejecting liquid (orifice plate, hereinafter), the opening area of the plate surface. Besides, the term xe2x80x9cejection opening centerxe2x80x9d is used to designate the center (gravity center) of geometry defined by the periphery of the head surface opening area.
In the present invention, the xe2x80x9cejection opening portionxe2x80x9d indicates the whole tubular opening area including the ejection opening, of members forming the ejection opening, such as an opening section disposed on the orifice plate, and includes the ejection opening. In the present invention, the xe2x80x9cliquid passagexe2x80x9d excludes the aforementioned xe2x80x9cejection openingxe2x80x9d except otherwise specified. In the present invention, an expression xe2x80x9cliquid ejecting directionxe2x80x9d may be used for convenience to designate the extension direction (thickness direction of the orifice plate for the head having an orifice plate) of the tubular sidewall forming the aforementioned xe2x80x9cejection opening portionxe2x80x9d.
Moreover, in the present invention, the xe2x80x9cgroovexe2x80x9d designates a concave open portion formed by an area locally remote from the ejection opening center (called xe2x80x9cgroove topxe2x80x9d hereinafter, in the present invention), and two areas locally near the ejection opening center adjacent to this area (called xe2x80x9cgroove basexe2x80x9d hereinafter, in the present invention), and corresponds to the shape having its thickness component in the aforementioned xe2x80x9cliquid ejecting directionxe2x80x9d. The term xe2x80x9cgroove center portionxe2x80x9d is used to designate the center (gravity center) of geometry defined by connecting the xe2x80x9cgroove topxe2x80x9d and two xe2x80x9cgroove basesxe2x80x9d adjacent to the top.